Fiction by Michael Robotham,
This story is told through the points of view of two London women, both expecting a baby around the same time. Meg is a mummy blogger with two young children and a "perfect" home and husband. Agatha is a supermarket stock girl who idolizes Meg and her family. The reader can tell there is something wrong about Agatha's interest in Meg, but the plot twists are pretty surprising!
I won't give anything away; just read it! Great book!